(println (sort-by first '(["5907" "string 1"] ["3012" "string 2"] ["897" "string 3"] ["1289" "string 4"] ["515" "string 5"])))
Standard input is empty
([1289 string 4] [3012 string 2] [515 string 5] [5907 string 1] [897 string 3])
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